High porosity/low permeability graphite bodies and process for the production thereof
View Patent ↗A method of forming a graphitic carbon body employs compression and resistance heating of a stock blend of a carbon material and a binder material. During molding of the body, resistance heating is accompanied by application of mechanical pressure to increase the density and carbonization of the resulting preform body. The preform can then be subjected to a graphitization temperature to form a graphite article.
1. A method of forming a carbon body having high porosity and ultra-low permeability, comprising the steps of:
(a) combining a carbon material and a binder material to form a stock mixture, wherein at least about 35% of the carbon material comprises particles having a maximum grain size of no greater than about 100 microns;
(b) resistively and compressively heating the stock mixture so as to form an at least partially carbonized preform body, the step of resistively and compressively heating including:
applying an electric current to the stock mixture to generate heat within the stock mixture; and
applying pressure of at least 35 kg/cm 2 to the stock mixture, thereby forming the carbon body having a porosity of greater than 10% and a permeability of less than 1.0 milli-darcys.
2. The method of claim 1 wherein at least about 50% of the carbon material comprises particles having a maximum grain size of no greater than about 100 microns.
3. The method of claim 1 wherein at least about 35% of the carbon material comprises particles having a maximum grain size of no greater than about 85 microns.
4. The method of claim 1 wherein at least about 35% of the carbon material comprises particles having a maximum grain size of no greater than about 75 microns.
5. The method of claim 1 wherein at least about 35% of the carbon material comprises particles in the form of a flour.
6. The method of claim 1 wherein at least about 35% of the carbon material comprises Compressible Particles having a maximum grain size of no greater than about 100 microns.
7. The method of claim 6 wherein Compressible Particles comprise graphite particles.
8. A method of forming a carbon body comprising the steps of:
(a) combining a carbon material and a binder material to form a stock mixture, wherein at least about 30% of the carbon material comprises Compressible Particles in the form of a flour;
(b) resistively and compressively heating the stock mixture so as to form an at least partially carbonized preform body, the step of resistively and compressively heating including:
applying an electric current to the stock mixture to generate heat within the stock mixture; and
applying pressure of at least 35 kg/cm 2 to the stock mixture, thereby forming the carbon body having a porosity of greater than 10% and a permeability of less than 1.0 milli-darcys.
9. The method of claim 8 wherein the Compressible Particles comprise graphite particles.
10. The method of claim 8 , wherein the binder material comprises pitches having coking yields of at least about 70%.
11. The method of claim 10 wherein the binder material comprises pitches having coking yields of at least about 80%.
12. The method of claim 8 , wherein said resistive and compressive heating step includes:
applying a first power level of electrical current for a first portion of said process time so as to heat the stock mixture to a first temperature; and
applying a second power level of electrical current for a second portion of said process time so as to heat the stock mixture to a second temperature, said second temperature being higher than said first temperature.
13. The method of claim 1 wherein step (b) includes forming an at least partially carbonized preform body in a mold box.
14. The method of claim 1 wherein step (b) includes forming an at least partially carbonized preform body while the stock mixture is stationary.
15. The method of claim 8 wherein step (b) includes forming an at least partially carbonized preform body in a mold box.
16. The method of claim 8 wherein step (b) includes forming an at least partially carbonized preform body while the stock mixture is stationary.